1. Field of the Invention
The invention relates to an object detection apparatus and a storage medium storing an object detection program, and more particularly, relates to an object detection apparatus that detects an object from a captured image and a storage medium storing an object detection program that detects an object from a captured image.
2. Description of Related Art
Recently, the number of vehicles provided with an object detection apparatus has been increasing. The object detection apparatus executes image processing on an image of a scene around the vehicle, which is captured by an in-vehicle camera, detects an object such as a pedestrian, and indicates the result of detection to a driver.
For example, an object determination apparatus has been proposed (refer to Japanese Patent Application Publication No. 2007-072665 (JP-A-2007-072665)). In the object determination apparatus, a plurality of templates in different modes are set for respective distances to objects to be determined; an object to be determined is detected from an image using the background differencing method or the saliency calculation method; a distance to the object is detected; a template corresponding to the distance is selected; and the object is determined by applying the template to the object that has been detected from the image as the object to be determined.
In a case where there are various postures of an object such as a pedestrian, it is possible to improve the accuracy of detecting the object by applying the templates in different modes, as in the object determination apparatus described in Japanese Patent Application Publication No. 2007-072665. However, as the number of the templates increases, the processing time is increased by applying all the templates to perform detection, although the detection accuracy can be increased by increasing the types of the templates.
Thus, an image recognition apparatus has been proposed (for example, refer to Japanese Patent Application Publication No. 2009-237897 (JP-A-2009-237897)). In the image recognition apparatus, a moving direction determination portion determines a moving direction of a target; a pedestrian pattern selection portion selects an image of a pedestrian moving in a moving posture and in the moving direction determined by the moving direction determination portion, from images of pedestrians moving in different moving directions, which are stored in advance in a pedestrian pattern storage portion. A recognition processing portion compares the pattern of the pedestrian moving in the selected moving direction, with the image pattern of the target to be recognized in an image captured by a camera, thereby recognizing a pedestrian.
Further, a candidate object area detection apparatus has been proposed (for example, refer to Japanese Patent Application Publication No. 2007-328630 (JP-A-2007-328630)). In the candidate object area detection apparatus, a plurality of different reference patterns for respective backgrounds of images (for example, reference patterns for sky, for a road, and for an area outside a road) are stored in a reference pattern database. A background area division portion divides the background of an input image using a vanishing point and traffic lane recognition. A reference pattern selection portion selects a reference pattern to be used by a candidate pedestrian area detection portion, according to a background area from which a determination area is cut out.
Also, a vehicle surrounding recognition system has been proposed (for example, refer to Japanese Patent Application Publication No. 2006-178652 (JP-A-2006-178652)). In the vehicle surrounding recognition system, an image processing portion retrieves a captured image for one frame from an image memory, and retrieves a vehicle speed v, a steering angle α, and an inclination angle β from a storage portion in synchronization with a frame rate. Further, the image processing portion obtains parameters for identifying a partial image by referring to LUT, based on the vehicle speed v, the steering angle α, and the inclination angle β, and stores the identified partial image in a frame memory. A pedestrian recognition processing portion retrieves the partial image stored in the frame memory, and determines the degree of similarity between the retrieved partial image and a standard pattern retrieved from a standard pattern portion.
In the image recognition apparatus described in Japanese Patent Application Publication No. 2009-237897, the pedestrian pattern to be used is selected based on the moving direction of the pedestrian. There is a problem that this technology cannot be applied when an object is static, for example, when a pedestrian is about to cross a road, and is static.
Also, in the candidate object area detection apparatus described in Japanese Patent Application Publication No. 2007-328630, the models for a road and for an area other than a road are selectively used. Attention is focused on variety of the background patterns, and attention is not focused on variety of postures of an object. Therefore, there is a problem that there is a possibility that robustness against a change in the posture may decrease. Also, because the risk degree of an area and the risk degree of the posture of an object are not taken into account, there is a problem that there is a possibility that the pedestrian model, the risk degree of which is not high for a driver, may be used, depending on the search range in which an object should be searched for.
Further, in the vehicle surrounding recognition system described in Japanese Patent Application Publication No. 2006-178652, the search range in which an object should be searched for is set based on the speed, steering angle, and the like of the host vehicle, and the risk degree, such as the possibility of collision, is not taken into account. There is a problem that there is a possibility that the pedestrian model, the risk degree of which is not high for a driver, may be used, depending on the search range in which an object should be searched for.